The present invention relates to an edge grinding unit for machines for working the edges of plates in general and of glass sheets in particular.
It is known that edge grinding units are currently applied to machines for working the edges of plates in general and of glass sheets in particular; in practice, such units are designed to produce a slight bevel at the edge of the plate.
This operation, which is absolutely necessary in the case of glass sheets which must subsequently be subjected to tempering, is designed to bevel the edge and is performed by means of a grinding wheel which can rotate inside a carousel element constituted by a cage formed by a plurality of rollers which rest against the edge of the plate, so that the grinding wheel forms the bevel in the intended manner.
In the solutions of the prior art, the edge grinding unit is generally constituted by an oscillating arm which supports a grinding wheel and is pushed by way of elastic means against the front edge of the incoming plate in order to bevel the front edge.
Then, as it continues its translational motion, the plate in practice moves the arm so that the rollers engage the longitudinal edge, without contact between the grinding wheel and the plate, until once the grinding wheel has reached the rear edge, such grinding wheel rises to work the rear edge. The movement of the plate, albeit very slow, in many cases does not allow to work the rear edge correctly, since the movement of the arm and therefore of the grinding wheel occurs in the opposite direction with respect to the advancement of the glass sheet.
In order to try to obviate this drawback, the edge grinding unit has been fitted on two linear guides so that when it makes contact with the glass sheet in order to work the front edge, the grinding wheel moves outwards and then follows said sheet, by means of the second slider, in order to work the rear edge thereof.
In the solution of the known art there are considerable masses in motion, since the unit also supports the motor that actuates the grinding wheel; moreover, such unit must follow the plate for a certain extent and perform the return stroke.
Accordingly, such edge grinding units force a reduction in the speed of translational motion of the plate, because the grinding wheel must follow, for a certain extent, the plate during the working of the rear edge thereof.
Moreover, it is necessary to keep a certain distance between the contiguous plates, because after a rear edge has been worked, the arm with the corresponding grinding wheel must be returned to the initial condition by means of the translational return motion of the entire movable unit, so that the grinding wheel returns to the initial conditions in order to engage the front edge of the next plate.
In this context, low operating speeds and considerable moving masses are involved and therefore collisions can occur between the grinding wheel and the plate being worked, with the consequent possibility of damaging said plate.
The aim of the invention is to eliminate the above mentioned drawbacks by providing an edge grinding unit for machines for working the edges of plates in general and of glass sheets in particular which allows to considerably increase operating speeds thereby increasing the speed of the translational motion of the plates being worked.
Within this aim, an object of the invention is to provide an edge grinding unit which allows to reduce the distance between two contiguous plates being worked, thus reducing idle times.
Another object of the present invention is to provide an edge grinding unit which allows to reduce the moving masses, thus allowing to apply lower pressures and reducing the impact that inevitably occurs when the plate contacts the grinding wheel; accordingly, the speed with which the glass sheet makes contact with the grinding wheel can be much higher, with the advantage of higher productivity of the machine.
Another object of the present invention is to provide an edge grinding unit which thanks to its particular constructive characteristics, is capable of giving the greatest assurances of reliability and safety in use.
This aim and these and other objects which will become better apparent hereinafter are achieved by an edge grinding unit for machines for working the edges of plates in general and of glass sheets in particular, which comprises, at least at one rim of a sheet being worked, a grinding wheel accommodated in a carousel element provided with a rotatable cage formed by a plurality of circumferentially distributed rollers, characterized in that it comprises means for supporting said grinding wheel which form, for said grinding wheel, a first oscillation pivot and a second oscillation pivot which are mutually spaced and are substantially perpendicular to the advancement plane of said plate.